Glycine betaine accumulation and induction of cold tolerance in strawberry (Fragaria X ananassa Duch.) plants

Endogenous glycine betaine levels in the leaves of strawberry (Fragaria X ananassa Duch.) plants were determined during cold acclimation and in response to exogenous abscisic acid (ABA) application. Glycine betaine levels in the leaves increased nearly two-fold after 4 weeks of cold acclimation treatment during which the cold tolerance of leaves increased from -5.8 to - 17°C. Exogenous application of ABA (100 μM) to plants triggered glycine betaine accumulation in unhardened plants. It also increased cold tolerance of leaves in both unhardened and cold-hardened plants. Similar to ABA, exogenous glycine betaine was effective in inducing cold tolerance in unhardened and cold-hardening plants. Exogenous application of glycine betaine (2 mM) to unhardened plants increased the cold tolerance of leaves almost two-fold within 72 h of application. In addition, it improved freezing survival and regrowth in whole plants. The results suggest that glycine betaine is involved in inducing cold tolerance both in response to exogenous ABA and during natural cold acclimation of strawberry plants.